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<p class="level0"><a name="NAME"></a><h2 class="nroffsh">NAME</h2>
<p class="level0">pcap_datalink - get the link-layer header type <a name="SYNOPSIS"></a><h2 class="nroffsh">SYNOPSIS</h2>
<p class="level0"><pre class="level0">
&#35;include &lt;pcap/pcap.h&gt;
int pcap_datalink(pcap_t *p);
</pre>

<p class="level0"><a name="DESCRIPTION"></a><h2 class="nroffsh">DESCRIPTION</h2>
<p class="level0"><span Class="bold">pcap_datalink()</span> returns the link-layer header type for the live capture or ``savefile&#39;&#39; specified by <span Class="emphasis">p</span>. 
<p class="level0">It must not be called on a pcap descriptor created by <span Class="bold">\%pcap_create(3PCAP)</span> that has not yet been activated by <span Class="bold">\%pcap_activate(3PCAP)</span>. 
<p class="level0"><span Class="emphasis"><a href="https://www.tcpdump.org/linktypes.html">https://www.tcpdump.org/linktypes.html</a></span> lists the values <span Class="bold">pcap_datalink()</span> can return and describes the packet formats that correspond to those values. 
<p class="level0">Do <span Class="bold">NOT</span> assume that the packets for a given capture or ``savefile`` will have any given link-layer header type, such as <span Class="bold">DLT_EN10MB</span> for Ethernet.  For example, the &quot;any&quot; device on Linux will have a link-layer header type of <span Class="bold">DLT_LINUX_SLL</span> even if all devices on the system at the time the &quot;any&quot; device is opened have some other data link type, such as <span Class="bold">DLT_EN10MB</span> for Ethernet. <a name="RETURN"></a><h2 class="nroffsh">RETURN VALUE</h2>
<p class="level0"><span Class="bold">pcap_datalink()</span> returns the link-layer header type on success and <span Class="bold">PCAP_ERROR_NOT_ACTIVATED</span> if called on a capture handle that has been created but not activated. <a name="SEE"></a><h2 class="nroffsh">SEE ALSO</h2>
<p class="level0"><a Class="bold" href="./pcap.html">pcap</a>(3PCAP), <a Class="bold" href="./pcap-linktype.html">pcap-linktype</a>(7) <p class="roffit">
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